Flaps-based microsurgery is routinely applied to reconstruct oral floor defects caused by oncologic resection. To prevent orocutaneous fistulae, flaps are frequently sutured with buccal vestibule mucosa after sacrificing the alveolar process. The patients suffered denture loss and irreversible structural damage. For reliable oral floor reconstruction with preservation of alveolar process, the authors introduced the flap “suture anchoring” technique. Oral floor, hemiglossal-oral floor, and tongue base-parapharyngeal wall-oral floor defects were included in this study. The flap anchoring technique involves structural oral floor reconstruction with a chimeric anterolateral thigh-free flap or radial forearm flap with adipofascial tissue extension. The dead space in oral floor is filled with vastus lateralis muscle or adipofascial tissue, then holes are drilled on the alveolar bone among tooth root, beneath the attached gingiva. Skin paddle is sutured with 4-0 sutures through the alveolar holes thus anchored to the mandible. By applying this technique, there was no wound infection or orocutaneous fistulae in all patients postoperatively, even experienced postoperative radiotherapy. In addition, a soft and natural jaw-tongue furrow could be formed to allow the free movement of tongue. Taken together, the flap anchoring technique offers a safe and reliable approach to recover oral function and preservation of occlusion.